The human microbiome can be defined as the microorganisms that reside within and on our bodies and how they interact with the environment. Recent research suggests that numerous mutually beneficial interactions occur between a human and their microbiome, including those that are essential for good health. Modern microbiological detection techniques have contributed to new knowledge about microorganisms in their human environment. These findings reveal that the microbiomes of the lung and gut contribute to the pathogenesis of asthma and allergy. For example, evidence indicates that the microbiome of the gut regulates the activities of helper T cell subsets (Th1 and Th2) that affect the development of immune tolerance. Moreover, recent studies demonstrate differences between the lung microbiomes of healthy and asthmatic subjects. The hygiene and biodiversity hypotheses explain how exposure to microorganisms is associated with asthma and allergy. Although those living in developed countries are exposed to fewer and less diverse microorganisms compared with the inhabitants of developing countries, they are experiencing an increase in the incidence of asthma and allergies. Detailed analyses of the human microbiome, as are being conducted under the auspices of the Human Microbiome Project initiated in 2007, promise to contribute insights into the mechanisms and factors that cause asthma and allergy that may lead to the development of strategies to prevent and treat these diseases.

Recurrent early life wheeze is not always asthma, and up to 50% of children are reported to remit. With reports of adult asthma symptom relapse, we assessed the prognosis of recurrent bronchial obstruction (rBO) through adolescence in the Environment and Childhood Asthma (ECA) prospective birth cohort study.The present study is based on data from investigations at ages 2, 10 and 16 years of 550 young people (52% males) attending at 16 years of age. Based on the presence of rBO from 0-2 years, defined as recurrent (at least two episodes) doctor-diagnosed wheeze, and asthma from 2-10 years and 10-16 years, defined as at least two episodes of doctor-diagnosed asthma, symptoms and medication use, prognosis of rBO was assessed. Bronchial hyperresponsiveness (BHR) was diagnosed by a metacholine provocation dose f8 mmol that caused 20% reduction in the forced expiratory volume in 1 s.At 10-16 years, 34% of the 143 rBO children had asthma. All children with rBO had reduced lung function compared with the never asthmatics. Of the rBO children in remission, 48.4% had asthma symptoms, medication use and/or BHR compared with 26.7% with never asthma (p,0.001).Only 34.3% of rBO children were without asthma symptoms, medication use or BHR by 16 years, possibly indicating future asthma risk.

Assessment of childhood asthma severity and asthma control encompasses heterogeneous clinical presentations. The relationship between patterns of asthma symptoms and objective measurements is poorly defined in paediatric asthma. This study includes 115 asthmatic schoolchildren, of which 31 were at inclusion defined as Problematic severe asthma because of inadequate asthma control in the presence of high-dose inhaled corticosteroid (HD-ICS) treatment and at least one other asthma controller drug. Two partially overlapping clinical outcomes were defined irrespective of severity classification (Exacerbations and Chronic persistent asthma) in patients with uncontrolled asthma. The same symptom criteria were used as for Problematic severe asthma, but disregarding current medication. Lung function, exhaled nitric oxide (FE(NO)), bronchial hyperresponsiveness, allergic sensitization and Quality of life (QoL) in the symptom subgroups were compared to children with well-controlled asthma. Multifactor analysis was performed to assess the relative explanatory power of clinical asthma presentations and of HD-ICS treatment on objective measurements. Whereas children included in the Exacerbations subgroup had objective features similar to patients with well-controlled asthma, the Chronic persistent asthma subgroup demonstrated significantly reduced lung function, increased immunoglobin E, allergic poly-sensitization and impaired QoL, similar to that in patients pre-defined as Problematic severe asthma. The presence of chronic asthma symptoms was a significant explanatory factor for reduced lung function, QoL and increased FE(NO) in multifactor analysis. Differences in objective measurements suggest that children with Chronic persistent asthma and those who are symptomatic predominantly during exacerbations may represent distinct phenotypes of childhood asthma with different clinical prognoses.

BHR at 10 years was a significant but modest predictor of active asthma 6 years later, with methacholine challenge being superior to exercise test.